Fix #13522 FP knownConditionTrueFalse after unsigned-to-signed conversion (danmar#7179)

Author: chrchr-github

lib/vf_analyzers.cpp

@@ -528,6 +528,8 @@ struct ValueFlowAnalyzer : Analyzer {
                 continue;
             if (exact && v.intvalue != 0 && !isPoint)
                 continue;
+            if (astIsUnsigned(tok) != astIsUnsigned(v.tokvalue))
+                continue;
             std::vector<MathLib::bigint> r;
             ValueFlow::Value::Bound bound = currValue->bound;
             if (match(v.tokvalue)) {

test/testcondition.cpp

@@ -4968,6 +4968,13 @@ class TestCondition : public TestFixture {
               "    }\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("void f(unsigned x) {\n" // #13522
+              "    unsigned u = x;\n"
+              "    int i = u - 0;\n"
+              "    if (i < 0) {}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void alwaysTrueInfer() {